Visual Field Deficits in Albinism in Comparison to Idiopathic Infantile Nystagmus.

PURPOSE: This is the first systematic comparison of visual field (VF) deficits in people with albinism (PwA) and idiopathic infantile nystagmus (PwIIN) using static perimetry. We also compare best-corrected visual acuity (BCVA) and optical coherence tomography measures of the fovea, parafovea, and circumpapillary retinal nerve fiber layer in PwA. METHODS: VF testing was performed on 62 PwA and 36 PwIIN using a Humphrey Field Analyzer (SITA FAST 24-2). Mean detection thresholds for each eye were calculated, along with quadrants and central measures. Retinal layers were manually segmented in the macular region. RESULTS: Mean detection thresholds were significantly lower than normative values for PwA (-3.10 ± 1.67 dB, P \u3c\u3c 0.0001) and PwIIN (-1.70 ± 1.54 dB, P \u3c 0.0001). Mean detection thresholds were significantly lower in PwA compared to PwIIN (P \u3c 0.0001) and significantly worse for left compared to right eyes in PwA (P = 0.0002) but not in PwIIN (P = 0.37). In PwA, the superior nasal VF was significantly worse than other quadrants (P \u3c 0.05). PwIIN appeared to show a mild relative arcuate scotoma. In PwA, central detection thresholds were correlated with foveal changes in the inner and outer retina. VF was strongly correlated to BCVA in both groups. CONCLUSIONS: Clear peripheral and central VF deficits exist in PwA and PwIIN, and static VF results need to be interpreted with caution clinically. Since PwA exhibit considerably lower detection thresholds compared to PwIIN, VF defects are unlikely to be due to nystagmus in PwA. In addition to horizontal VF asymmetry, PwA exhibit both vertical and interocular asymmetries, which needs further exploration

Feasibility and Clinical Utility of Hand-held Optical Coherence Tomography in Children with Retinoblastoma

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023

Cerebral malaria: insight into pathology from optical coherence tomography

AbstractWe aimed to investigate structural retinal changes in malarial retinopathy (MR) using hand-held optical coherence tomography (HH-OCT) to assess its diagnostic potential. Children with MR (n = 43) underwent ophthalmoscopy, fluorescein angiography and HH-OCT during admission, 1-month (n = 31) and 1-year (n = 8) post-discharge. Controls were comatose patients without malaria (n = 6) and age/sex-matched healthy children (n = 43). OCT changes and retinal layer thicknesses were compared. On HH-OCT, hyper-reflective areas (HRAs) were seen in the inner retina of 81% of MR patients, corresponding to ischaemic retinal whitening on fundus photography. Cotton wool spots were present in 37% and abnormal hyper-reflective dots, co-localized to capillary plexus, in 93%. Hyper-reflective vessel walls were present in 84%, and intra-retinal cysts in 9%. Vascular changes and cysts resolved within 48 h. HRAs developed into retinal thinning at 1 month (p = 0.027) which was more pronounced after 1 year (p = 0.009). Ischaemic retinal whitening is located within inner retinal layers, distinguishing it from cotton wool spots. Vascular hyper-reflectivity may represent the sequestration of parasitized erythrocytes in vessels, a key CM feature. The mechanisms of post-ischemic retinal atrophy and cerebral atrophy with cognitive impairment may be similar in CM survivors. HH-OCT has the potential for monitoring patients, treatment response and predicting neurological deficits.</jats:p

Ophthalmology

To characterize the genotypic and phenotypic spectrum of foveal hypoplasia (FH). Multicenter, observational study. A total of 907 patients with a confirmed molecular diagnosis of albinism, PAX6, SLC38A8, FRMD7, AHR, or achromatopsia from 12 centers in 9 countries (n = 523) or extracted from publicly available datasets from previously reported literature (n = 384). Individuals with a confirmed molecular diagnosis and availability of foveal OCT scans were identified from 12 centers or from the literature between January 2011 and March 2021. A genetic diagnosis was confirmed by sequence analysis. Grading of FH was derived from OCT scans. Grade of FH, presence or absence of photoreceptor specialization (PRS+ vs. PRS-), molecular diagnosis, and visual acuity (VA). The most common genetic etiology for typical FH in our cohort was albinism (67.5%), followed by PAX6 (21.8%), SLC38A8 (6.8%), and FRMD7 (3.5%) variants. AHR variants were rare (0.4%). Atypical FH was seen in 67.4% of achromatopsia cases. Atypical FH in achromatopsia had significantly worse VA than typical FH (P < 0.0001). There was a significant difference in the spectrum of FH grades based on the molecular diagnosis (chi-square = 60.4, P < 0.0001). All SLC38A8 cases were PRS- (P = 0.003), whereas all FRMD7 cases were PRS+ (P < 0.0001). Analysis of albinism subtypes revealed a significant difference in the grade of FH (chi-square = 31.4, P < 0.0001) and VA (P = 0.0003) between oculocutaneous albinism (OCA) compared with ocular albinism (OA) and Hermansky-Pudlak syndrome (HPS). Ocular albinism and HPS demonstrated higher grades of FH and worse VA than OCA. There was a significant difference (P < 0.0001) in VA between FRMD7 variants compared with other diagnoses associated with FH. We characterized the phenotypic and genotypic spectrum of FH. Atypical FH is associated with a worse prognosis than all other forms of FH. In typical FH, our data suggest that arrested retinal development occurs earlier in SLC38A8, OA, HPS, and AHR variants and later in FRMD7 variants. The defined time period of foveal developmental arrest for OCA and PAX6 variants seems to demonstrate more variability. Our findings provide mechanistic insight into disorders associated with FH and have significant prognostic and diagnostic value

Visual Abnormalities and Sensory Integration in Infantile Nystagmus

Introduction: Individuals with albinism and IIN demonstrate retinal structural abnormalities. However, there are no consistent functional retinal differences apparent using full-field flash electroretinography (ffERG). This thesis aims to investigate abnormalities in albinism and IIN at: (i) early stages of visual processing (i.e. retinal deficits) using ffERG; (ii) late stages of visual processing, where the brain integrates visual inputs with other sensory to control posture, using Computerized Dynamic Posturography (CDP). Methods: ffERG and OCT were used to measure functional and structural retinal deficits, respectively. Binocular pupil tracker was used to characterise nystagmus to investigate its effect on ffERG responses. CDP was used to evaluate sensory organization during postural control. Results: Patients with IIN had significant smaller a- and b-wave amplitudes under photopic condition compared to healthy controls. However, individuals with albinism were relatively normal. Test-retest showed that ffERG testing is mostly reliability despite nystagmus being present. Photopic a-wave amplitudes were correlated with combined photoreceptor layer thickness and scotopic S.F. b-wave amplitudes were correlated with the inner nuclear layer thickness. Patients with albinism and IIN have relative good overall postural control. However, both groups present lower visual score and higher somatosensory score than controls. The albinism group also had a higher vestibular sensory score. Conclusion: Reductions of photopic a- and b-wave amplitudes in IIN indicate a subclinical retinal deficit, which has not been previously detected. Interestingly, participants with albinism did not show abnormalities probably due to hypopigmentation shifting the baseline of ERG responses into normal ranges. Correlations between ffERGs and OCT measurements suggest ffERG may contain useful information in albinism and open up an interesting field for future study. Brain plasticity can rearrange the weighting of sensory inputs in both patient groups with the albinism group attaching a stronger weighting to vestibular cues than the other two groups

Our current understanding of clinical characteristics and the genetics of patients with albinism

Introduction: Albinism is a heterogenous disease with variable phenotypic and genotypic presentations. Diagnosis can be challenging and clinical evaluation strategies vary. Areas covered: This review examines the phenotypic and genotypic characteristics of albinism and discusses evaluation strategies used to assess its variable clinical presentations. Additionally, it explores the challenges faced by clinicians in diagnosing albinism and issues related to genetic testing, interpretation and subsequent counseling of affected patients and their families. It is important to note that although current management of albinism is mainly supportive and focuses on optimizing vision, there are emerging therapies with promising translational benefit. Expert opinion: Ongoing research in the field of albinism is benefiting from recent advances, particularly in retinal imaging and phenotyping. Similarly, access to advanced technologies like next-generation and long-read sequencing has improved diagnostic accuracy for previous cases with missing heritability. Deeper genotyping and phenotyping as well as multicentre collaborative approaches have allowed better understanding of genotype-phenotype correlations. There is still a need for more research on the psychosocial aspects of albinism. Encouraging involvement of patients and the public in determining research priorities in this area is essential for a better understanding of the psychosocial impact on individuals with albinism

Visual Field Deficits in Albinism in Comparison to Idiopathic Infantile Nystagmus

Purpose: This is the first systematic comparison of visual field (VF) deficits in people with albinism (PwA) and idiopathic infantile nystagmus (PwIIN) using static perimetry. We also compare best-corrected visual acuity (BCVA) and optical coherence tomography measures of the fovea, parafovea, and circumpapillary retinal nerve fiber layer in PwA. Methods: VF testing was performed on 62 PwA and 36 PwIIN using a Humphrey Field Analyzer (SITA FAST 24-2). Mean detection thresholds for each eye were calculated, along with quadrants and central measures. Retinal layers were manually segmented in the macular region. Results: Mean detection thresholds were significantly lower than normative values for PwA (−3.10 ± 1.67 dB, P Conclusions: Clear peripheral and central VF deficits exist in PwA and PwIIN, and static VF results need to be interpreted with caution clinically. Since PwA exhibit considerably lower detection thresholds compared to PwIIN, VF defects are unlikely to be due to nystagmus in PwA. In addition to horizontal VF asymmetry, PwA exhibit both vertical and interocular asymmetries, which needs further exploration.</p

Retinal imaging technologies in cerebral malaria: a systematic review.

BackgroundCerebral malaria (CM) continues to present a major health challenge, particularly in sub-Saharan Africa. CM is associated with a characteristic malarial retinopathy (MR) with diagnostic and prognostic significance. Advances in retinal imaging have allowed researchers to better characterize the changes seen in MR and to make inferences about the pathophysiology of the disease. The study aimed to explore the role of retinal imaging in diagnosis and prognostication in CM; establish insights into pathophysiology of CM from retinal imaging; establish future research directions.MethodsThe literature was systematically reviewed using the African Index Medicus, MEDLINE, Scopus and Web of Science databases. A total of 35 full texts were included in the final analysis. The descriptive nature of the included studies and heterogeneity precluded meta-analysis.ResultsAvailable research clearly shows retinal imaging is useful both as a clinical tool for the assessment of CM and as a scientific instrument to aid the understanding of the condition. Modalities which can be performed at the bedside, such as fundus photography and optical coherence tomography, are best positioned to take advantage of artificial intelligence-assisted image analysis, unlocking the clinical potential of retinal imaging for real-time diagnosis in low-resource environments where extensively trained clinicians may be few in number, and for guiding adjunctive therapies as they develop.ConclusionsFurther research into retinal imaging technologies in CM is justified. In particular, co-ordinated interdisciplinary work shows promise in unpicking the pathophysiology of a complex disease

Reliability and Recommended Settings for Pediatric Circumpapillary Retinal Nerve Fiber Layer Imaging Using Hand-Held Optical Coherence Tomography

To investigate feasibility and reliability of 3-dimensional full circumpapillary retinal nerve fiber layer (cpRNFL) analysis in children, with and without glaucoma, without the use of sedation and to recommend a protocol for hand-held optical coherence tomography use.A cohort of pediatric glaucoma patients and normal children were imaged with hand-held optical coherence tomography to assess the feasibility of obtaining full cpRNFL. Two consecutive scans were acquired in a smaller sample to investigate test-retest repeatability and interassessor reproducibility. The cpRNFL thickness was assessed in four quadrants, at several visual angles from the optic nerve center.Scanning was attempted in both eyes of 90 children with pediatric glaucoma and 180 controls to investigate feasibility (mean age, 6.98 ± 4.42 years). Scanning was not possible in 68 eyes of glaucoma children mainly owing to nystagmus, unclear optical media, or high refractive errors. Where three-dimensional imaging was possible, success at obtaining full cpRNFL was 67% in children with glaucoma and 89% for controls. Seventeen children with pediatric glaucoma and 34 controls contributed to reliability analysis (mean age, 6.3 ± 3.63 years). For repeatability intraclass correlation coefficients across quadrants ranged from 0.63 to 0.82 at 4° and improved to 0.88 to 0.94 at 6°. Intraclass correlation coefficients for reproducibility were also highest at 6° (>0.97 across all quadrants).We demonstrate that acquisition and measurement of cpRNFL thickness values using 3-dimensional hand-held optical coherence tomography volumes in awake children is both feasible and reliable and is optimal at 6° from optic nerve center.Our recommended protocol provides guidance on how pediatric optic nerve pathologies are managed by clinicians.</p